problem was, brittany eldridge was married to another man then brittany found out she was pregnant andt was just weeks before her due date that strategy struck. investigators would home in on the two men in brittany's life but was either capable of murder? here's andrea canning with "deadly circumstances." >> imagine all of your phone conversations being recorded for posterity? how would you feel. what secrets would they tell? >> why are you talking like you're trying to hide something? >> reporter: this story begins here at a suburban office outside knoxville, tennessee. looks a lot like any office in america. but when workers here talked on their desk phones, every word was captured. >> she always looks like she's about to kill be. >> and, oh, the stories they told. unfiltered and intimate with details about office romances. >> oh, my god, he was so hot. >> and in one heartbreaking case, maybe even clues about a murder. >> this was a real whodunit. >> norman clark loves sports. his mother says he was a top athlete and a good son too. >> he was a loving, hard worker, caring person. >>